Disclosed in co-pending U.S. patent applications Ser. Nos. 60/575982 and 60/614747 are alkanes having absorbance of 0.01 to 1.0 cm−1 at a wavelength of 193 nm and methods for their preparation. Alkanes of such low aborbance are highly suitable for use as immersion fluids in the new field of immersion photolithography. Disclosed therein are methods which combine distillation, contact with a variety of adsorbents, and handling in an oxygen-minimized atmosphere which are required to achieve the unprecedented high levels of transparency of the alkanes provided therein.
As a general rule, fabricators of electronic chips do not wish to develop capabilities in chemical purification on site. It is insufficient, therefore, to prepare such highly transparent alkanes for use in electronics fabrication and other critical uses if the very high transparency levels which make them useful cannot be maintained during shipment and subsequent storage in the customer's fabrication facility.
H. Hirata et al, JP(Kokai)56-74439, discloses use of adsorbents in contact with hydrocarbon fuels—comprising substantially alkanes—in a storage container for said fuels, the purpose of the adsorbents being to maintain the purity and fuel value of said fuels. The purpose of the adsorbents is to remove oxidation products. No mention is made of the atmosphere. No attempt is made to exclude air.
Rohwer et al., J. High Res. Chrom., 16, pp. 561 ff, (1993) disclose “ultra-high purity” hexane prepared by fractional column distillation. In a study to establish the influence of storage conditions on maintenance of hexane purity it is concluded that “purging with inert gas” did “not appreciably alter shelf life” and is discouraged because of added possibilities of contamination.
In Technical Bulletin AL-134, Aldrich Chemical Company discusses handling of the air-sensitive reagents borane complexes, organoboranes, borohydrides, Grignard reagents, and organo-aluminums, lithiums, and zincs using special sealed bottles which exclude oxygen. The bottles are flushed with nitrogen before filling.
Containers for volatile and reactive reagents, including those sensitive to the air are known in the art. Technical Bulletin AL-136 of the Aldrich Chemical Company describes the “Sure/Pac(™)” cylinder system, a brass or stainless steel vessel for storing highly reactive organo-metallics. Cottingham, U.S. Pat. No. 4,362,250 discloses a container for storing reactive or volatile material having a dual-neck seal. Also disclosed are Aldrich Sure-seal(™) glass bottles which are in common commercial use.